Leftovers of the Solar System
Besides the planets and moons, our solar system is filled with countless smaller objects. These are the leftover building blocks from when the solar system formed 4.6 billion years ago. The most well-known of these are asteroids, comets, and meteors.
Asteroids: The Rocky Remnants
An asteroid is a small, rocky body that orbits the Sun.
Composition: They are made of rock, metals, and other minerals. They are like small, irregularly shaped planets.
Location: Most asteroids are found in the Asteroid Belt, a region of space located between the orbits of Mars and Jupiter. Scientists think that Jupiter's immense gravity prevented a planet from forming in this region, leaving the rocky debris behind.
Size: They can range in size from a few feet across to hundreds of miles in diameter. The largest asteroid is named Ceres, and it's so big it's also classified as a dwarf planet.
Comets: The Icy Visitors
A comet is a small body of ice, rock, and cosmic dust that orbits the Sun in a highly elliptical (oval-shaped) path.
Composition: They are often called 'dirty snowballs'. They are a mixture of ice (water ice, dry ice), frozen gases, rock, and dust.
The Tail: When a comet's orbit brings it close to the Sun, the Sun's heat causes the ice to vaporize, releasing gas and dust. The solar wind pushes this gas and dust away from the comet, forming a long, glowing tail that always points away from the Sun. Comets actually have two tails: a bluish gas tail and a white dust tail.
Location: Most comets come from two very distant regions of the solar system: the Kuiper Belt (a region beyond Neptune) and the Oort Cloud (a vast, spherical cloud of icy bodies that surrounds the entire solar system).
Meteors: The 'Shooting Stars'
This is where the terminology can be a bit confusing. It's all about where the object is.
Meteoroid: A meteoroid is a small piece of rock or dust that is floating through space. They are usually pieces broken off from asteroids or comets.
Meteor: When a meteoroid enters the Earth's atmosphere, friction with the air causes it to heat up and burn with a streak of light. This glowing streak is called a meteor, or a 'shooting star'. Most meteors are no bigger than a grain of sand and burn up completely in the mesosphere.
Meteorite: If a meteoroid is large enough to survive its fiery passage through the atmosphere and lands on the Earth's surface, the remaining piece is called a meteorite.
So, it's a meteoroid in space, a meteor in the atmosphere, and a meteorite on the ground.